You want a comedy that's off and running with a fresh sense of discovery, that builds on its own exhilaration and leaves an audience giddy with glee?

Well, "Me, Myself & Irene" ain't got it.

You can't have everything.

A Jim Carrey movie is always worth seeing, even if it doesn't re-create the guileless shock and scintillation of "Dumb and Dumber." A Farrelly brothers movie is always worth seeing, too, even if it doesn't have a chance of making the next American Film Institute list of 100 best comedies ("There's Something About Mary" was No. 21 on the just-released list, and deservedly so).

"Me, Myself & Irene" is a schizophrenic comedy in more ways than the Farrellys bargained for, or seem to understand.

It is a comedic fandango on the "Jekyll and Hyde" myth, where the good and evil personalities of one character are in love with the same woman.

It is a comedy of hostility that also wants to be loved. You can't have it both ways.

Carrey plays a Rhode Island state trooper with a split personality. One of them, a sweet lunk named Charlie, is so spineless that he wishes his bride well when she becomes infatuated with another man almost before Charlie has a chance to finish carrying her across the threshold.

When other insults pile up and he finally can no longer take it, the second personality emerges. It is the rogue cop Hank, a small-town Dirty Harry.

One of the best things about Carrey's performance is the Clint Eastwood imitation he does as Hank, whispered malice that comes from the back of the throat and goes for the jugular.

Like "Beauty and the Beast," the ugly creature is sexier than the nice prince, which is where Irene, who's caught between them, comes in.

The object of both Charlie and Hank's affection is Renee Zellweger ("Jerry Maguire") as Irene, a down- to-earth young woman with an interestingly shady background. A big- town girl, she has underworld ties that come to the surface when she is detained in poor little Rhode Island -- the Farrellys' home turf, by the way -- on a traffic violation.

San Franciscans love every opportunity to exercise their self-righteous indignation, and "Me, Myself & Irene" will hand them another. One running joke that takes racial stereotypes and turns them inside out is so astoundingly off-the-wall that you have to give the bighearted Farrellys the benefit of the doubt.

The man Charlie's wife (not Irene) runs off with is African American and a dwarf. That's the joke, and it's a relief that he's played by the glintingly confident Tony Cox. The couple will abandon their triplet boys, leaving them with Charlie, who is in denial that they're obviously not his. After the kids grow into genius-IQ teenagers -- overgrow is more like it -- the running joke is the number of times they can say the word "mother--." It was funny the first half-dozen times.

Carrey is not the only officer of the law in this film who can play good cop-bad cop without a partner. There are other two-faced cops who seem to be in a much less inspired movie. "Me, Myself & Irene" has the stop-and-go quality of a jalopy as it lurches among good Charlie and bad Hank, which can be terrific, and the others, which definitely is not. So much explanation is required that a folksy, offscreen narrator is required.

The film ends with the most curious outtakes ever seen: still shots of all the Farrelly friends whose bit parts were trimmed even more or eliminated altogether. The list should have been longer. I hope the final shot was not intended as the insult to the audience it seems to be.

Carrey does have wonderful opportunities in fits and starts. His transformation, in a single take, from Charlie to Hank is a glorious parody of Fredric March in 1931's "Dr. Jekyll and Mr. Hyde." The inevitable moment later when Charlie must fight Hank, however, seems only that: inevitable.

Among his other successful bits is a wildly funny episode of dry mouth brought on by taking the medication that will keep Charlie from turning into the beast.

I like gross-out comedy as much as any other pimply-faced masturbator, and some of the moments when it occurs here have that old Farrelly hair-gel gloss, including a couple of the penis jokes.

Carrey himself provides the biggest flash from a major star since Rudolf Nureyev in "Valentino," a flash, that is, for any moviegoer who saw that film before projectionists clipped out that particular frame for their own collections.